1. Field of the Invention
The present invention relates generally to an apparatus and method for monitoring water quality. More particularly, the present invention relates to an apparatus and method for monitoring water quality using the ventilatory behavior and body movement of aquatic organisms.
2. Description of the Related Art
Ventilatory responses are often some of the first prelethal symptoms exhibited by animals to environmental stressors. Continued, abnormal ventilatory behavior, such as rapid, shallow, or erratic breathing, can indicate physiological damage that may be irreversible. Changes in the ventilatory behavior of fish have been shown to be a reliable indicator of accidental toxic spills or xe2x80x9cslugsxe2x80x9d of pollutants in wastewater and drinking water systems. Accordingly, ventilatory biomonitoring systems can serve as an early indicator of impending damage to aquatic ecosystems and possible harm to humans.
The technological means are readily available to log and display ventilatory signals for subsequent analysis. As a result, there are a considerable number of studies that have examined ventilatory behavior of fish and other aquatic organisms. A large number of substances at lethal levels have been shown to elicit ventilatory responses relatively quickly. For many pollutants, a significant response was often generated in less than one hour of exposure to concentrations approaching the 96-hour LC50 (the concentration at which fifty percent of the organisms expire within 96 hours of exposure). Studies performed using subacutely toxic samples of effluents or individual pollutants (concentrations well below the reported LC50 concentration) often documented responses within one to ten hours of exposure.
Although a variety of organisms have been examined for this purpose, including crayfish, aquatic insect larvae, and bivalves, most research in aquatic ventilatory behavior has used freshwater fish species. This is largely because fish are generally more ecologically xe2x80x9cvisiblexe2x80x9d in their importance in aquatic systems and many species (particularly the salmonids and centrarchids) have large opercular flaps that yield relatively clear ventilatory signals for measurement and evaluation.
The ventilatory parameters in fish that have been shown to be affected by toxicity include ventilatory rate (opercular movement over time), depth of ventilation (amplitude), coughing or gill purge rate, and erratic episode frequency due to sudden movement of the organism. Most commonly, changes in just ventilatory rate, as opposed to the other parameters just mentioned, have been used as a bioindicator of toxic conditions. The depth of ventilation and gill purge or cough rate, however, have been reported to be more sensitive indicators of toxicity for some compounds.
Changes in ventilatory rate are often determined by manual examination of the peaks per unit area on a strip-chart recording. Depth of ventilation or signal amplitude is similarly measured from top to bottom of the waveform on the strip chart. Cough rate has been more difficult to determine even with manual examination of a strip chart as several different types of coughs may be present, each with its own characteristic waveform pattern. Also, without the use of simultaneous video techniques, the actual occurrence of a cough is not always clear.
Accordingly, one object of the present invention is to provide an apparatus for automated biomonitoring of water quality.
Another object of the present invention is to be able to include behavioral parameters such as the depth of ventilation, cough rate, and whole body movement of an aquatic organism in addition to ventilatory frequency data in the automated biomonitoring of water quality.
A related object of the present invention is to be able to further include water quality characteristics such as dissolved oxygen, pH, temperature, and conductivity in the biomonitoring of water quality.
Another object of the present invention is to provide improved waveform processing of data signals from aquatic organisms to reduce spurious data signals.
Another object of the present invention is to be able to provide an array of biomonitor exposure chambers with an integral water delivery and drain system for improved ventilatory signal data collection and biomonitor operation.
Another object of the present invention is to be able to provide a programmable alarm response that includes automated water sampling and optional remedial action such as isolation of the water pollution source.
These and other objects will be apparent from the following description.
According to one aspect of the invention, an apparatus for monitoring and evaluating water quality includes an exposure chamber for housing an aquatic organism and containing water to be monitored, and electrodes for sensing electrical signals generated by the organism during ventilatory behavior and body movement in the water being monitored. Electrical signals picked up by the electrodes are supplied to an automatic controller, which determines one or more ventilatory and body movement parameters based on the signals from the electrodes. The controller compares the parameters with corresponding thresholds to determine when the water to which the organism is exposed has caused physiological stress to the organism.
The controller may determine a wide variety of ventilatory and body movement parameters. In a preferred embodiment, the controller determines at least the ventilatory frequency, the average ventilatory depth, and the cough rate of the organism.
In one embodiment, signals received from the electrodes may be corrected to compensate for the effect of the conductivity of the water on signal amplitude.
The system may further include various devices operative in response to a determination of a water quality problem by the controller. For example, it may include an alarm mechanism which generates an alarm, a sample device which collects samples of the water being monitored for subsequent analysis, or a diverting mechanism for diverting the water being monitored to a storage tank and preventing the water from being discharged into the environment.
According to another aspect of the present invention, a method of evaluating water quality comprises measuring electrical signals generated by an aquatic organism disposed in water to be monitored, determining one or more ventilatory and body movement parameters of the organism based on the signals, and comparing the parameters with corresponding thresholds to determine when the water to which the organism is exposed has caused physiological stress to the organism.
The monitoring and determination of ventilatory and body movement parameters of an aquatic organism by an automated controller as taught in the present invention provides for continuous, around-the-clock monitoring of water quality with fast signal processing and good reproducibility of results, which are otherwise not possible with manual methods of biomonitoring. The present invention can employ a plurality of ventilatory and body movement parameters to provide greater detection sensitivity and accuracy over systems using a one-parameter analysis, and the present invention is readily integrated with effluent control systems for wastewater treatment plants, factories, and other possible sources of pollutants. The invention also may be used to monitor and evaluate the quality of a body of water such as a lake or stream, or the inlet to a potable water treatment facility, providing a detection capability of inadvertent or intentional toxic contamination of the water source. Such contamination could otherwise go undetected without the present invention until human health is effected and traced to the source of contaminated drinking water. In addition, the exposure chamber of the present invention provides improved biomonitoring of aquatic organisms with a top-bottom electrode arrangement, uniform mixing of the water prior to organism exposure, and reduced water stratification within the chamber.